More funerals and memorial services were held Thursday in Newtown, Connecticut for victims of the second-deadliest school shooting in U.S. history.

The latest victims laid to rest were as young as six years old -- some of the 20 children killed in Friday's mass shooting. Twenty-six people died when a gunman opened fire on students and staff at an elementary school before taking his own life. Authorities believe the gunman also killed his mother before driving to the school.

Investigators are trying to determine a motive for all the killings.

U.S. Attorney General Eric Holder is traveling to the small town later Thursday to meet with law enforcement officials examining the mass shooting.

The attack has renewed a national debate over gun violence and gun control laws, and Holder's trip comes shortly after a meeting with Vice President Joe Biden to discuss measures to curb shooting assaults.

On Wednesday, President Barack Obama chose Biden to lead an effort to write a set of concrete proposals to address gun violence. Biden said Thursday that the Obama administration is "absolutely committed" to curbing gun violence.

Obama called Wednesday for Congress to reinstate an assault weapons ban that lapsed in 2004.

A poll released Wednesday indicates the mass shooting has led to a shift in views on gun laws.

The CNN/ORC International poll says 52 percent of those surveyed favor "major restrictions on guns or making all guns illegal."

The researchers say that is a five-point rise from a poll conducted in August, shortly after a mass shooting at a Colorado movie theater left 12 dead, and six people people were killed in a shooting at a Sikh temple in Wisconsin.